Embodiments of the present invention generally relate to an apparatus and a method for verifying dispense of a fluid. More specifically, the embodiments relate to an apparatus and a method for verifying fluid dispense in an automated instrument.
Automated instruments are available to perform a number of tasks. One such automated instrument is an analytical instrument. An analytical instrument can perform tests, such as medical diagnostic tests, on a sample. For example, such tests may identify the AIDS virus in a blood sample or other item of interest in a biological sample.
To perform such tests, an analytical instrument may mix the biological sample with a substance, such as a reagent and the like. In some embodiments, these reagents may be fluids. The fluids may be supplied to the biological sample within the medical instrument by a fluid system. The fluid system may include a source of fluid, a pump, a dispense nozzle and a conduit fluidly connecting those elements. The source of fluid may be a container and the like. The pump operates to move fluid from the container toward the dispense nozzle through the conduit. The sample, which may be held in a suitable container, is positioned adjacent the dispense nozzle. When the pump is operated, fluid from the container leaves the nozzle and enters the sample container. Movement of the fluid into the container, if desired, can cause the fluid and the sample to mix.
Illustrating further by example, a given instrument may perform a blood analysis. The instrument adds a predetermined volume of a fluid to a predetermined volume of a blood sample. The fluid reacts with the blood sample. Because of the reaction between the sample and the fluid, an electromagnetic signal or light is sent from the mixture of sample and fluid. A detector in the instrument sees or reads the light sent from the mixture. Appropriate elements of the instrument, such as a computer and the like, interpret the information obtained by the detector and provide an operator with information about the blood sample.
In order for this instrument to perform as intended and to give accurate results, it is desirable that a specific, predetermined amount or volume of fluid be mixed with the sample. If too much or too little fluid is added to the sample, the light sent from the mixture may be different from the proper light sent from the mixture when the predetermined volume of fluid is added. The different light sent from the mixture is interpreted by the computer in the same way as the proper light. Therefore, the computer may give inaccurate information to the operator of the instrument.
The possibility of inaccurate information being given by an instrument is a concern. For example, the test performed may be to see if a unit of blood were infected with the AIDS virus. Assuming that the blood is infected with the AIDS virus, adding too little or too much fluid to the blood sample may result in the instrument telling the operator that the unit of blood is not infected with the AIDS virus.
Many things can cause the wrong amount of fluid to be added to the sample. For instance, the conduit may contain a bubble. The conduit itself may be bent or damaged. The pump may not function properly. A drop of fluid may form on an end of the dispense nozzle. These causes may not be detected by simply monitoring the length of time of pump operation or of fluid leaving the dispense nozzle. Accordingly, it can be appreciated that it is desirable to have an element in the instrument for verifying that the proper, predetermined amount of fluid has left the dispense nozzle during operation of the analytical instrument.